The present invention relates generally to turbines, and more particularly to a turbine inner shroud and a turbine assembly containing an inner shroud.
Turbine assemblies include, without limitation, turbine sections of steam turbines and compressor and/or turbine sections of gas turbines. Steam and gas turbines are used, among other purposes, to power electric generators, and gas turbines also are used, among other purposes, to propel aircraft and ships. A steam turbine has a steam path which typically includes, in serial-flow relationship, a steam inlet, a turbine, and a steam outlet. A gas turbine has a gas path which typically includes, in serial-flow relationship, an air intake (or inlet), a compressor, a combustor, a turbine, and a gas outlet (or exhaust nozzle). Compressor and turbine sections include at least one circumferential row of rotating blades. The free ends or tips of the rotating blades are surrounded by a stator casing. The radial gap between the blade tips and the stator casing is made small for increased efficiency of the turbine.
Typically, as shown in prior-art FIG. 1, a metal inner shroud 2 (such as one made of Inconel.RTM.), has been attached through mating slots to a circumferential segment of an outer shroud block 4 of the stator casing 6 and is spaced apart from the blade tips 8. The metal inner shroud 2 is subject to heat distortion because of high thermal gradients in the shroud area of the turbine. Such heat distortion places the inner shroud 2 and the outer shroud block 4 under significant mechanical stresses. What is needed is an inner shroud which is more heat resistant and an attachment for the inner shroud which is subject to less mechanical stress.